1. Technical Field
The present invention relates to an organic electro-luminescence (EL) device with filter including an organic EL element and, also, a method of repairing the same.
2. Background Art
In recent years, organic EL displays have been regarded as being usable as display devices. An organic EL display is constituted by an organic EL element having characteristics such as low-voltage driving, self-light-emission, and high-speed response. Such an organic EL display is of a self-light-emission type, which eliminates the necessity of provision of a back light which is required in a liquid crystal display, thereby enabling reduction of the product thickness, power consumption and cost.
Herein, a structure of the organic EL display will be described simply.
FIG. 6 is a schematic cross-sectional view illustrating the structure of a conventional organic EL display. In FIG. 6, an anode 2, an EL layer 3, and a cathode 4 are formed on a glass substrate 1 in which the respective components are formed thereon in the mentioned order. The EL layer 3 contains an organic compound having the function of emitting light by being supplied with a voltage or by being supplied with external energy such as UV light. Further, the EL layer 3 emits light in any light-emission color, such as red, green, and blue colors, by being supplied with external energy. In addition thereto, in some cases, there may be provided a color filter 5 for improving the color-creation ability of the display. As illustrated in FIG. 6, an organic EL display 6 is structured.
Subsequently, light emission from the organic EL display 6 will be described. When a direct-current voltage is applied between the two electrodes (between the anode 2 and the cathode 4), holes 7 and electrons 8 are supplied to the EL layer 3. Holes 7 and electrons 8 combine with each other in the EL layer 3 to generate energy, which excites electrons in the organic compound contained in the EL layer 3. When the excited electrons are brought into a ground state, they emit energy as light to the outside, which causes the EL layer 3 to emit light. Therefore, in order to cause the EL layer 3 to emit light uniformly, it is necessary that holes 7 and electrons 8 are uniformly supplied to the EL layer 3.
An interval L between the anode 2 and the cathode 4 is about 1 micrometer and therefore is significantly narrow, thereby forming a fine structure. Therefore, in cases where the thicknesses of the electrodes (the anode 2 and the cathode 4) are non-uniform or a foreign substance is intruded between the electrodes, the EL layer 3 may be caused to have portions having non-uniform thicknesses, during the processing for fabricating the organic EL display 6. In such cases, the EL layer 3 has lower electric resistances at its portions with smaller thicknesses and, therefore, holes 7 and electrons 8 are actively supplied thereto, which induces leak currents for making the light emission from the EL layer 3 non-uniform, thereby inducing non-uniform pixels.
Further, in cases where the foreign substance 9 is large, complete conduction (a short-circuit) is established between the anode 2 and the cathode 4 due to bite and the like of the foreign substance 9 therebetween, which prevents the occurrence of combination of holes 7 and electrons 8 in the EL layer 3, thereby causing the EL layer 3 to perform no light emission to induce non-lighting pixels (hereinafter, referred to as extinct points).
If a plurality of non-uniform pixels and extinct points are induced in the organic EL display 6, this significantly degrades the image quality and the display quality of the display, which makes it impossible to make a shipment of the product. In order to address this, it is necessary to find and repair non-uniform pixels and extinct points. As a repairing method therefor, there is a method which, at first, detects weak leak light generated from an organic EL display as a result of application of a reverse-bias voltage thereto and, then, burns off the electrodes at the periphery thereof.
There will be described a case of detecting, through color filters, weak leak light generated as a result of application of such a reverse-bias voltage, with reference to FIG. 7.
FIG. 7 is a conceptual view of weak leak-light detection through conventional color filters. Referring to FIG. 7, when a reverse-bias voltage from a power supply 10 is applied to an anode 4 and a cathode 4 on a glass substrate 1, leak light 12 is generated from a current-leak generating portion 11. The leak light 12 passes through a color filter 5 and, thereafter, is detected by a weak-light detection camera 13. The detection of leak light from an organic EL display 6 having color filters is performed on pixels (hereinafter, referred to as red-filter pixels, green-filter pixels, and blue-filter pixels) through respective color filters for a red color, a green color, and a blue color.
Next, there will be described, in detail, light transmittance characteristics of color filters. It is assumed that there are provided the same anode, the same cathode, the same EL layer, the same glass substrate, and the same power supply, for each of the red-filter pixels, the green-filter pixels, and the blue-filter pixels. Further, it is assumed that, when the same reverse-bias voltage is applied thereto, the red-filter pixels, the green-filter pixels, and the blue-filter pixels induce respective current-leak generating portions, such that the current-leak generating portions in the respective pixels have the same area and the same leak light intensity. Even in this case, the red color filter, the green color filter, and the blue color filter have different light transmittance characteristics and, therefore, the leak lights passed through the respective color filters have different light intensities and different spectra.
Hereinafter, transmittance characteristics of a red color filter, a green color filter, and a blue color filter will be described, by exemplifying liquid-crystal-intended color filters.
FIG. 8A is a view illustrating a spectral transmittance characteristic of Toptical as shown in “'94 Market of Liquid-crystal Display Peripheral Materials and Chemicals”, CMC Corporation, Jun. 20, 1994 (the first printing published), and FIG. 8B is a view illustrating a CIE chromaticity of TOPTICAL, as shown in “'94 Market of Liquid-crystal Display Peripheral Materials and Chemicals”, CMC Corporation, Jun. 20, 1994 (the first printing published). FIG. 9 is a view illustrating a spectral transmittance characteristic of a color-filter pigment-dispersed type resist, as shown in “'94 Market of Liquid-crystal Display Peripheral Materials and Chemicals”, CMC Corporation, Jun. 20, 1994 (the first printing published).
As illustrated in FIG. 8A, the display-intended color filters have precise specifications around the wavelengths to be passed therethrough, but their characteristics are varied in other regions. Weak light emission from the EL layer is induced by current leak and, therefore, exhibits a spectrum including a near-infrared range, as disclosed in Japanese Patent Laid-open Publication No. 2006-323032. Accordingly, their characteristics in longer-wavelength ranges are important. In comparing between FIGS. 8A and 8B and FIG. 9, at a maximum wavelength of 700 nm, the Toptical of FIG. 8A has a higher transmittance for B (blue) than that for G (green), while the color-filter pigment-dispersed type resist of FIG. 9 has a higher transmittance for G (green) than that for B (blue). Further, both of them have a higher transmittance for R (red) than those for G (green) and B (blue), at the wavelength 700 nm.
Further, when repairing is performed on defective portions (non-uniform pixels, extinct points) which have been detected according to the aforementioned method, the repairing is influenced by the spectral transmittance characteristics of the color filters. This is because, when laser is directed thereto, the transmittance characteristics are largely varied, depending on whether the defective portions exist on red-filter pixels, green-filter pixels, or blue-filer pixels. For example, in cases where the laser wavelength is a YAG twofold wavelength (532 nm), even when the transmittance characteristics of the color filters are as the characteristic of FIG. 9, their transmittance for G (green) is higher than those for R (red) and B (blue). Accordingly, referring to the characteristics of FIGS. 8A and 8B, the laser passed through the green color filter has higher intensity, but the laser passed through the red-color filter and the laser passed through the blue-color filter have lower intensity. Further, the green color filter absorbs a smaller amount of laser, while the red color filter and the blue color filter absorb larger amounts of laser.